Car engine piston cooling is an important technology for improving the compression ratio and suppressing the deformation of pistons.It is well known that thermal conductivity improves dramatically through the use of heat pipes in computers and air conditioners.However, the heat pipes in general use have not been used for the cooling of engines because the flow of gas and liquid is disturbed by vibration and the thermal conductivity becomes excessively low.We therefore developed an original heat pipe and conducted an experiment to determine its heat transfer coefficient using a high-speed reciprocation testing apparatus.Although the test was based on a single heat pipe unit, we succeeded in improving the heat transfer coefficient during high-speed reciprocation by a factor of 1.6 compared to the heat transfer coefficient at standstill. This report describes the observed characteristics and the method of verification.In the future, we plan to examine the application of this approach to engine pistons.